Thermo-couple



ture is large.

U NE

MATTHEW A. HUNTER, OF TROY, NEW] YORK, ASSIGNOR TO DRIVER-HARRIS COM- IPANY, OF HARRISON, NEW JERSEY, A CORPORATION OF NEW JERSEY.

THEBJIO-COUPLE.

No Drawing.

T 0 all whom it may concern:

' Be it known that I, MATTHEW A. HUNTER,

.duce such a thermo-couple in which the electromotive force per degree rise in tempera- It further has for its object to produce a couple in which the electromotive force temperature curves are approxi mately straight lines with no inversion points. It further has for its object to produce a couple in which the materials are reproducible and maintain their calibration. It further has'for its object to produce a thermo-couple in which the materials used are capable of being rolled into rods or drawn into wires.

The following is a description of an embodiment of my invention, attaining the ob jects abovereferred to.

The couples now on the market, which are most widely used, are constantan (Cu. 60, Ni. 40) with iron, and nickel-aluminum with nickel-chromium.

The former is a satisfactory thermo-couple below 1000 C. The chief cause of its failure lies in the rapid oxidation of the constantan element of the thermo-couple and the deterioration of the couple at higer temperatures. The electromotive force of the couple is high and varies almost as a straight line function with the temperature. Further, it holds its calibration well under successive heatings and coolings.

The latter couple can be used for higher temperatures, (possibly 1250 (l). The E. M. F. temperature curve is, however, not as good as that of the iron-constantan couple. Further, the original calibration curve is not so satisfactorily maintained.

I have discovered that if a proper amount of chromium is added to the constantan of the iron-constantan couple the melting point of the alloy is materially increased, being about 1400 C. and that it is more resistant Specification of Letters Patent.

Patented Oct. 11, 1921.

Application filed February 17, 1920. Serial No. 359,466.

' nickel vary considerably from those of constantan, but alloys beyond certain ranges are useless for the reason that outside of those ranges the materials do not have a sufficiently high melting point or are not sufficiently resistant to oxidation, or the E. M. F. temperature curves are not approximately straight lines or have inversion points. Thus, 25 parts copper, 75 parts nickel and 5 to 10 parts chromium have marked inversion points, while a 100 part concentrate of 25 to 10 parts copper with 75 to 90 parts nickel, to which v5 to 10 parts of chromium are added, have far from linear E. M. F. temperature curves.

I have discovered that if to a 100 part concentrate composed of 50 to 7 5 parts of copper and 50 to 25 parts of nickel from 5 to 80 parts of chromium are added, a Very desirable product for my purposes is attained. The maximum E. M. F. would probably be obtained by using an alloy parts copper and 40 parts nickel, and adding to that concentrate 5 to 30 parts of chromium. With an element composed of this product against iron, the E. M. F. temperature curve is substantially a straight line. The values obtained fora difference in temperature of 800 C. between hot and cold junctions vary from 23.63 to 28.52 millivolts according to the composition of the wire, the latter value corresponding to copper 75, nickel 25, chro mium 20. In order to increase the E. M. F. of the couple and'also to increase the resistance to oxidation of the other element, I prefer to substitute for the iron an alloy composed of nickel and chromium of a composition substantially like that used in the nickel aluminum-nickel chromium couple now in use, namely, about nickel 100, chromium 10. This not only increases the melting point and resistance to oxidation of the corresponding element, but increases the tan couple, whose melting point and resistance to oxidation were much inferior.

Both elements of the couple when made as above described are reproducible and maintain their calibration to a remarkable extent, the couple giving a substantially linear E. M. F. curve with no inversion points. The materials are capable of being rolled into rods or drawn into wires.

As will be evident to those skilled in the art, my invention permits of various modifications without departing from the spirit thereof or the scope of the appended claims.

What I claim is:

1. In a thermo-couple, a concentrate containing from 75 to 50 parts copper and 25 to 50 parts nickel alloyed with from 5 to 30 parts chrominum.

2. In a thermocouple, two elements producing when heated or cooled a substantially linear electromotive force temperature curve, one of said elements consisting of an alloy of copper, nickel and chrominum, which is refractory and highly resistant to oxidation and with the other element results in approximately straight line electromotive force temperature curves.

3. In a thermo-couple, two elements producing when heated or cooled a substantially linear E. M. F. temperature curve, one of said elements consisting of an alloy of copper, nickel and chromium, said alloy having from 105 to 130 parts, at least 50 of which are copper and at least 25 of which are nickel, the copper and nickel amounting to 100 parts. I v

4. In a thermo-couple, two elements producing when heated or cooled a substantially linear E. M. F. temperature curve, one of said elements consisting of an alloy of copper, nickel and chromium, said alloy having from 105 to 110 parts, at least 50 of which are copper and at least 25 of which are nickel, the copper and nickel amounting to 100 parts.

5. In a thermo-couple, ducing when heated or tially linear E. M. F. temperature curve, one of said elements consisting of an alloy of copper, nickel and chromium, said alloy having from 105 to 110 parts, about 60 of which are copper and about 40 of which are nickel, the copper and nickel amounting to about 100 parts.

6. In a thermo-couple, ducing when heated or cooled a substantially linear E. M. F. tem erature curve, one of said elements consistlng of an alloy of copper, nickel and chromium, said alloy two elements prohaving from 105 to 130 parts, at least 50 of which are copper and at least 25 of which are nickel, the copper and nickel amounting two elements procooled a substanto parts, the other element being composed of an alloy of nickel and chromium.

MATTHEW A. HUNTER. 

